Twiglet is a ~50 cm, 19-DoF 3D-printed biped with a wooden-ball head, two round digital eyes, a printed hair piece under a felt hat, a leaf kilt and two small arms with grippers. It is inspired by Open Duck Mini (v2), and reuses some of its open-source parts (legs, neck, electronics) under Apache-2.0 — see NOTICE.
Hardware → · BOM → · Print → · Assemble → · Simulation → · Contribute →
Status: simulation only. Nothing has been printed or built yet, so every number below is from MuJoCo and mesh checks. Photos and videos of a real build are TODO.
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| Complete, back view | Head + hair piece v3.44 | Head shells and nose |
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| Legs on the trunk | 3-DoF arms (STS3032) | Head inside: Pi, eyes, ballast |
- Head: a new wood-textured ball head (v3.30) with a hollow nose and two 2.1" round touch LCDs as eyes (ESP32-S3; firmware in
experiments/twiglet_eyes/), using a 3-servo neck (Open Duck Mini v2-compatible). - Hair piece: one printed piece (v3.44, 186 g at 4.5 % infill) that pins and keys onto the head; a felt hat goes over it.
- Body: a slim torso cone with a 10-petal leaf kilt, shin covers and boots (body v3.34, 50 STLs).
- Arms: two 3-DoF arms (shoulder, elbow, gripper) on Feetech STS3032 micro bus servos, powered from a 6 V buck regulator.
- Simulation and checks: MuJoCo model, open-loop gait parameters, standing, push and neck-load tests, plus collision and print-file checks on the real meshes. All of it runs from this repo.
| Category | Item | Specification |
|---|---|---|
| Body | Size | about 340 × 276 × 499 mm (feet to hair top, rest pose; hat not modelled) |
| Body | Mass (sim model) | 2.753 kg; head 0.814 kg including the 25 g ballast and the hair piece |
| Motion | Joints | 19: 10 legs + 3 neck (13 × Feetech STS3215), 6 arms (Feetech STS3032) |
| Computing | Main board | Raspberry Pi Zero 2W (as upstream) |
| Sensing | IMU | BNO055 (as upstream) |
| Interaction | Eyes | 2 × Waveshare ESP32-S3-Touch-LCD-2.1 (480 × 480 round), UART from the Pi |
| Power | Battery | 2S 18650 (2 cells) + 2S BMS; 5 V UBEC for logic and eyes; 6 V buck for the arm servos |
| Printing | Printer used for the checks | Bambu P1S (every part fits 256 × 256 × 256 mm), PLA / PETG / optional TPU |
Full parts list with links and prices: docs/BOM.md (CSV: docs/BOM.csv). Several prices are still TODO.
From experiments/, model experiments/twiglet_sim/models/twiglet_v3_v334_wig344.xml (body v3.34 + head v3.30 + hair v3.44), re-run from this repo on 5 Oct 2026:
| check | result | pass criterion |
|---|---|---|
| standing margin (crouch 0.10) | 50.5 mm | no fall, > 30 mm |
| head + arm motion (e-margin) | 34.1 mm | ≥ 30 mm |
| neck-pitch static hold | 0.232 N·m = 2.11× the STS3215 rating | ≥ 2× |
| main gait, 20 randomized trials | 19/20 at 0.206 m/s | ≥ 19/20 |
| main gait, 20 held-out seeds | 18/20 at 0.206 m/s | ≥ 18/20 |
| efficient gait, 20 randomized trials | 20/20 at 0.156 m/s | ≥ 19/20 |
| hair vs arms inside the soft limits | 0 / 0 / 0 (yaw 0 / −45 / +45) | 0 |
| 315-pose head range | 154/315 poses with any contact, 0 hair-only | ≤ ~154, 0 hair-only |
| eye coverage by the hair | 0 / 0 triangles | 0 |
| print files | watertight, 1 body, fit the P1S | all |
The gaits are 12-parameter open-loop/PD vectors (BEST_WALK_PARAMS_v334r1.npy, BEST_WALK_EFF_PARAMS_v333r1.npy; see experiments/twiglet_sim/walk_search.py), not ONNX RL policies like upstream's. Training a policy with Open_Duck_Playground is TODO.
| Resource | Purpose |
|---|---|
| docs/BOM.md | Parts list (upstream columns + our extra parts) |
| docs/print_guide.md | Which stock parts are still used, plus the print settings of every new part (some are required: the sims assume them) |
| docs/assembly_guide.md | 15-step build with rendered step images |
| print/mods/Twiglet/ | New STLs (print-oriented), Blender sources and build scripts |
| mini_bdx/robots/twiglet_v334/ | MuJoCo model (MJCF + meshes) |
| experiments/ | Every simulation and geometry check, how to run it, and the reference results |
| docs/configure_motors.md, docs/sim2real.md, docs/prepare_robot.md | Servo IDs, sim-to-real notes, how the model was made |
| docs/upstream/ | The upstream Open Duck Mini v2 docs, unchanged, for reference |
For the stock Open Duck Mini v2 parts use upstream's Onshape CAD and BOM. The onboard runtime is upstream's Open_Duck_Mini_Runtime (TODO: add the arm servos and the eye UART).
Every file is under GitHub's 100 MB limit. Over 25 MB: print/mods/Twiglet/source/blender/body_v334.blend (59 MB). The head v3.30 .blend (194 MB) is not included; its rebuild scripts are in print/mods/Twiglet/source/scripts/head_v3.30/.
Twiglet is inspired by Open Duck Mini (v2) by Antoine Pirrone (apirrone) and the Open Duck Mini contributors (see thanks.md), sponsored by HuggingFace and Pollen Robotics. Some stock Open Duck Mini v2 parts, wiring diagrams and docs are reused here under the Apache License 2.0; NOTICE lists exactly which files are theirs, unmodified or modified. Thanks also to Rhoban for BAM, and to the MuJoCo, trimesh, PyVista and Blender projects.
This project is not affiliated with or endorsed by Pollen Robotics, HuggingFace or the Open Duck Mini project.
Copyright 2026 Mike Holborn (DreamMachina).
The new material in this repository is licensed under the Apache License 2.0. The Open Duck Mini v2 material stays under its own Apache-2.0 terms and copyright; see NOTICE. Contributions are accepted under the same licence (see CONTRIBUTING.md).